The present invention relates to a device and method for attaching soft tissue such as a ligament or ligament graft to a bone. The device and method are particularly useful for fixing the soft tissue within a tunnel formed in a bone proximate to the natural point of attachment of the soft tissue.
The complete or partial detachment of ligaments, tendons or other soft tissues from their associated bones within the body are relatively commonplace injuries, particularly among athletes. Such injuries are generally the result of excess stress being placed on these tissues. Tissue detachment may occur as the result of an accident such as a fall, overexertion during a work related activity, during the course of an athletic event or in any one of many other situations and/or activities. If, however, the ligament or tendon is completely detached from its associated bone or bones, or if it is severed as part of a traumatic injury, partial or permanent disability may result. Fortunately, a number of surgical techniques; exist for reattaching such detached tissues and/or completely replacing severely damaged tissues.
One such technique involves the reattachment of the detached tissue using "traditional" attachment devices such as metal staples and cancellous bone screws. Such "traditional" attachment devices have also been used to attach tendon or ligament substitutes (often formed of autogenous tissue harvested from elsewhere in the body) to the desired bone or bones.
Another technique is described in detail in U.S. Pat. No. 4,950,270 entitled "Cannulated Self-Tapping Bone Screw", issued to Bowman et al. on Aug. 21, 1990, and specifically incorporated herein by reference. In this technique, the anterior cruciate ligament in a human knee, for example, is replaced and/or repaired by forming bone tunnels through the proximal tibia and/or distal femur at the points of normal attachment of the anterior cruciate ligament. A ligament graft with a bone block on at least one of its ends is sized to fit within the bone tunnels. A suture is then attached to the outer end of each bone plug and sutures on opposite ends of the graft structure are passed through the femoral and tibial bone tunnels. The femoral plug and the tibial plug are then inserted into their respective bone tunnels behind the sutures. The sutures are then drawn tight simultaneously in opposite directions. This procedure places the bone plugs in the desired position, and imparts the desired degree of tension to the ligament or ligament substitute. Finally, a bone screw is inserted between each bone plug and the wall of its associated bone tunnel so as to securely lock the bone plug in position by a tight interference fit.
Another common ligament attachment technique is described in U.S. Pat. No. 5,645,588 entitled "Graft Attachment Device," issued to Graf et al. on Jul. 8, 1997, and in U.S. Pat. No. 5,769,894 entitled "Graft Attachment Device and Method of Attachment," issued to Ferragamo on Jun. 23, 1998. This method uses a button-like device that rests on the outside of a bone, covering at least part of the opening to a bone tunnel. The button is first sutured to a portion of a ligament graft at a distance from the button, in effect suspending the graft from the button. The button-suture-graft construct is then pulled through the bone tunnel and the button is seated outside the far end of the tunnel with the ligament graft suspended within the tunnel.
U.S. Pat. No. 5,356,413, entitled "Surgical Anchor and Method for Deploying the Same," issued to Martins et al. on Oct. 18, 1994, discloses a surgical anchor device having a metal anchor body with nickel-titanium alloy arcs located on a leading end of the body. One transverse bore on the leading end is used to place a suture which is used to pull the anchor into a bone tunnel. A second transverse bore located in the trailing end of the anchor. The ligament graft may be directly connected to the second bore, or the ligament graft may be suspended from the second bore by suture thread.
The ligament fixation schemes described above have not been entirely successful. For example, rigid attachment using "traditional" attachment devices such as staples, sutures and screws often cannot be maintained even under normal tensile loads. Also, the use of sharp screws to create a locking interference fit between a bone plug and a bone tunnel can be problematic. For one thing, there is always the possibility of damaging the ligament during insertion of the screw. In addition, it can be difficult to maintain the desired tension on the ligament or repair material during insertion of the screw.
Non-rigid fixation schemes, such as suspending a ligament graft from a suture button, also have drawbacks. Because the graft structure is not rigidly fixed within the bone tunnels, movement of the graft structure can disrupt the healing process.
Despite the various ligament fixation methods known in the art, it would still be desirable to provide a ligament fixation device and method that can rigidly fix a ligament graft within a bone tunnel at a desired ligament tension for a time sufficient to allow the ligament graft to permanently fix itself to the bone.